Pipes made of polyethylene have become popular in transporting water and gas, for instance in houses and in municipal water distribution. Polyethylenes having a high or medium density are frequently used in such pipes due to their good mechanical properties and ability to withstand pressure. Especially pipes made of multimodal polyethylene having a density of from about 947 to 953 kg/m3 have become increasingly popular. Such pipes and polymer compositions suitable for making them are disclosed, among others, in WO-A-00/01765, WO-A-00/22040, EP-A-739937, EP-A-1141118, EP-A-1041113, EP-A-1330490 and EP-A-1425344. A co-pending European Patent Application No. 06020872.5 discloses flexible pressure-resistant pipes made of bimodal polyethylene and having a density of from 940 to 947 kg/m3.
Such pipes, however, suffer from the disadvantage that the pipes made of HDPE materials are not flexible enough so that they could be wound to a coil which is preferred in certain applications. Flexible pipes have been made from linear low density polyethylene and they are disclosed, among others, in EP-A-1574549. However, such pipes often lack the sufficient mechanical properties that are required from pipes used for transporting water or gas at high pressure.